Effects of Explant Types and Phytohormones on Azarshahr Red Onion Micropropagation

The Azarshahr red onion (Allium cepa L.), also known as “Germez Azarshahr”, is a native variety widely cultivated in northwestern Iran and highly valued for its culinary and pharmacological properties. Seed propagation of this variety is not economical as it results in uneven sowing and excessive consumption of resources such as water. In addition, the yield has significantly decreased due to abiotic and biotic stresses. Since there are no reports on the in vitro regeneration of commercially important onion varieties in Iran, this study aimed to evaluate the impact of different explants (mature embryo, basal plate and leaf) and different doses of auxin growth regulators -Naphthaleneacetic Acid (NAA), Picloram, and ۲,۴-dichlorophenoxyacetic acid (۲,۴-D)- both individually and together with ۶-benzylaminopurine (BAP), on callus induction and regeneration of this variety to improve its use in molecular breeding and genetic engineering programs. The experiments were arranged in a completely randomized design with three replicates, and the data were analyzed using ANOVA and Duncan’s multiple-range test (p≤۰.۰۵). The results indicated that the basal plate (۵۰.۶۵%) and mature embryo (۴۰.۲۲%) were the most effective for callus induction in different media. ۲,۴-D demonstrated superior efficiency in callus induction and production of high-quality embryogenic calli. The maximum callus induction rates were ۸۱.۶۷% for basal plates and ۷۱.۳۳% for mature embryos using Gamborg (B۵) medium with BAP + ۲,۴-D (۲+۱ mg L-۱). Furthermore, fifteen shoots were successfully regenerated from each basal plate callus at a frequency of ۶۱.۵۵% using B۵ medium with BAP + NAA (۱.۵+۰.۱ mg L-۱). This optimized protocol is suitable for rapid clonal propagation, germplasm preservation, and conducting genetic transformation studies of the Azarshahr red onion variety.

Keywords:

Allium cepa , basal plate , callus , growth regulators , mature embryo